cppwinrt/README.md

# The C++/WinRT language projection

C++/WinRT is an entirely standard C++ language projection for Windows Runtime (WinRT) APIs, implemented as a header-file-based library, and designed to provide you with first-class access to the modern Windows API. With C++/WinRT, you can author and consume Windows Runtime APIs using any standards-compliant C++17 compiler.

* Documentation: https://aka.ms/cppwinrt
* NuGet package: http://aka.ms/cppwinrt/nuget
* Visual Studio extension: http://aka.ms/cppwinrt/vsix
* Wikipedia: https://en.wikipedia.org/wiki/C++/WinRT

# Building C++/WinRT

Don't build C++/WinRT yourself - just download the latest version here: https://aka.ms/cppwinrt/nuget

## Working on the compiler

If you really want to build it yourself, the simplest way to do so is to run the `build_test_all.cmd` script in the root directory. Developers needing to work on the C++/WinRT compiler itself should go through the following steps to arrive at an efficient inner loop:

* Open a dev command prompt pointing at the root of the repo.
* Open the `cppwinrt.sln` solution.
* Choose a configuration (x64, x86, Release, Debug) and build projects as needed.

If you are working on an ARM64 or ARM specific issue from an x64 or x86 host, you will need to instead:

* Open the `cppwinrt.sln` solution
* Build the x86 version of the "cppwinrt" project first
* Switch to your preferred configuration and build the test binaries and run them in your test environment

## Comparing Outputs

Comparing the output of the prior release and your current changes will help show the impact of any updates. Starting from
a dev command prompt at the root of the repo _after_ following the above build instructions:

* Run `build_projection.cmd` in the dev command prompt
* Run `build_prior_projection.cmd` in the dev command prompt as well
* Run `prepare_versionless_diffs.cmd` which removes version stamps on both current and prior projection
* Use a directory-level differencing tool to compare `_build\$(arch)\$(flavor)\winrt` and `_reference\$(arch)\$(flavor)\winrt`